The Elastic Load Balancer helps ensure traffic is evenly distributed across servers. Very helpful when dealing with high traffic loads and potential denial of service conditions whether accidental or intentional. AWS ELB comes in three flavors, Application Load Balancer ALB, Network Load Balancer NLB, and the Classic Elastic Load Balancer.
With the AWS ELB service, inbound traffic is distributed to multiple EC2 instances in a group. Without the ELB in place, traffic can end up hitting only one instance, increasing the likelihood of experiencing traffic beyond their capacity to handle it. An affected service could suffer a Denial of Service (DoS) when overloaded with traffic. ELBs help mitigate this be smartly distributing the traffic across healthy nodes. This helps to increase fault tolerance, or the system’s ability to recover from performance degradation and failures.